const Crypto = {};

(function() {

	var base64map = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

	// Global Crypto object
	// window.Crypto = {};

	// Crypto utilities
	var util = Crypto.util = {

		// Bit-wise rotate left
		rotl: function(n, b) {
			return (n << b) | (n >>> (32 - b));
		},

		// Bit-wise rotate right
		rotr: function(n, b) {
			return (n << (32 - b)) | (n >>> b);
		},

		// Swap big-endian to little-endian and vice versa
		endian: function(n) {

			// If number given, swap endian
			if (n.constructor == Number) {
				return util.rotl(n, 8) & 0x00FF00FF |
					util.rotl(n, 24) & 0xFF00FF00;
			}

			// Else, assume array and swap all items
			for (var i = 0; i < n.length; i++)
				n[i] = util.endian(n[i]);
			return n;

		},

		// Generate an array of any length of random bytes
		randomBytes: function(n) {
			for (var bytes = []; n > 0; n--)
				bytes.push(Math.floor(Math.random() * 256));
			return bytes;
		},

		// Convert a string to a byte array
		stringToBytes: function(str) {
			var bytes = [];
			for (var i = 0; i < str.length; i++)
				bytes.push(str.charCodeAt(i));
			return bytes;
		},

		// Convert a byte array to a string
		bytesToString: function(bytes) {
			var str = [];
			for (var i = 0; i < bytes.length; i++)
				str.push(String.fromCharCode(bytes[i]));
			return str.join("");
		},

		// Convert a string to big-endian 32-bit words
		stringToWords: function(str) {
			var words = [];
			for (var c = 0, b = 0; c < str.length; c++, b += 8)
				words[b >>> 5] |= str.charCodeAt(c) << (24 - b % 32);
			return words;
		},

		// Convert a byte array to big-endian 32-bits words
		bytesToWords: function(bytes) {
			var words = [];
			for (var i = 0, b = 0; i < bytes.length; i++, b += 8)
				words[b >>> 5] |= bytes[i] << (24 - b % 32);
			return words;
		},

		// Convert big-endian 32-bit words to a byte array
		wordsToBytes: function(words) {
			var bytes = [];
			for (var b = 0; b < words.length * 32; b += 8)
				bytes.push((words[b >>> 5] >>> (24 - b % 32)) & 0xFF);
			return bytes;
		},

		// Convert a byte array to a hex string
		bytesToHex: function(bytes) {
			var hex = [];
			for (var i = 0; i < bytes.length; i++) {
				hex.push((bytes[i] >>> 4).toString(16));
				hex.push((bytes[i] & 0xF).toString(16));
			}
			return hex.join("");
		},

		// Convert a hex string to a byte array
		hexToBytes: function(hex) {
			var bytes = [];
			for (var c = 0; c < hex.length; c += 2)
				bytes.push(parseInt(hex.substr(c, 2), 16));
			return bytes;
		},

		// Convert a byte array to a base-64 string
		bytesToBase64: function(bytes) {

			// Use browser-native function if it exists
			if (typeof btoa == "function") return btoa(util.bytesToString(bytes));

			var base64 = [],
				overflow;

			for (var i = 0; i < bytes.length; i++) {
				switch (i % 3) {
					case 0:
						base64.push(base64map.charAt(bytes[i] >>> 2));
						overflow = (bytes[i] & 0x3) << 4;
						break;
					case 1:
						base64.push(base64map.charAt(overflow | (bytes[i] >>> 4)));
						overflow = (bytes[i] & 0xF) << 2;
						break;
					case 2:
						base64.push(base64map.charAt(overflow | (bytes[i] >>> 6)));
						base64.push(base64map.charAt(bytes[i] & 0x3F));
						overflow = -1;
				}
			}

			// Encode overflow bits, if there are any
			if (overflow != undefined && overflow != -1)
				base64.push(base64map.charAt(overflow));

			// Add padding
			while (base64.length % 4 != 0) base64.push("=");

			return base64.join("");

		},

		// Convert a base-64 string to a byte array
		base64ToBytes: function(base64) {

			// Use browser-native function if it exists
			if (typeof atob == "function") return util.stringToBytes(atob(base64));

			// Remove non-base-64 characters
			base64 = base64.replace(/[^A-Z0-9+\/]/ig, "");

			var bytes = [];

			for (var i = 0; i < base64.length; i++) {
				switch (i % 4) {
					case 1:
						bytes.push((base64map.indexOf(base64.charAt(i - 1)) << 2) |
							(base64map.indexOf(base64.charAt(i)) >>> 4));
						break;
					case 2:
						bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 0xF) << 4) |
							(base64map.indexOf(base64.charAt(i)) >>> 2));
						break;
					case 3:
						bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 0x3) << 6) |
							(base64map.indexOf(base64.charAt(i))));
						break;
				}
			}

			return bytes;

		}

	};

	// Crypto mode namespace
	Crypto.mode = {};

})();

module.exports = Crypto;
